As the background art of the technical field, JP-T-2009-501902 (PTL 1) describes that “there are provided an inspection system, a circuit, and a method for enhancing flaw detection by taking measures of saturated levels of an amplifier and an analog/digital circuit as a limiting factor of a measurement detection range of an inspection system, and there are provided an inspection system, a circuit, and a method for enhancing flaw detection by reducing thermal damage to large particles due to a dynamic change in an incident laser/beam power/level at which incident laser beams are supplied to a specimen during scanning of surface inspection taking measures of saturated levels of an amplifier and an analog/digital circuit as a limiting factor of a measurement detection range of an inspection system” (see Abstract).
In addition, as described in JP-A-2001-144357 (PTL 2), means for switching and applying a predetermined voltage with respect to a Pockels cell is provided as means for driving the Pockels cell.
Further, a foreign matter inspection device for a semiconductor wafer detects a minute flaw that is present on a wafer surface, and outputs the number, a coordinate, or a size of the flaw. Due to the miniaturization of a semiconductor process, there is a demand for improvement of detection sensitivity in the foreign matter inspection device. There is a method for achieving high intensity of illumination light as an example of means for improving the detection sensitivity. However, when irradiation is performed with the illumination light having high intensity, large foreign matter having a size that exceeds hundreds of nm is broken. In this specification, this phenomenon is referred to as explosive fracture. Since fragments from the explosive fracture are spread over a specimen surface and a flawed region of the specimen is increased, an inspection power (intensity of illumination light used for inspection) needs to be limited.
In the specification of U.S. Pat. No. 7,787,114 (PTL 3), a technology of dynamically controlling an inspection power during inspection using Pockels cells is disclosed. In PTL 1, normally, while inspection is performed with high sensitivity by high-power irradiation, the inspection power is reduced during the inspection on foreign matter and the vicinity thereof such that explosive fracture is avoided in a case where there is large foreign matter.